In conventional fuel injectors, an adjustment sleeve on which a restoring spring is braced that acts on the valve-closure member is pressed into a spring pocket opening. When pressing the adjustment sleeve in, there is the danger that shavings will form on the adjustment sleeve and on the wall of the spring pocket opening.
German Patent No. DE 41 25 155 describes a fuel injector in which the restoring spring is pressed into a spring pocket opening and retained in the spring pocket opening by radially directed tension. The pressing-in depth of the restoring spring defines the magnitude of the spring force acting on the valve-closure element. The diameter of the restoring spring in an active spring region is smaller than that of the spring pocket opening, while the diameter of a cylindrical clamping region facing away from the valve-closure element is larger than that of the spring pocket opening.
A particular disadvantage of the construction having a self-clamping spring described in German Patent No. 41 25 155 is the high installation force. Moreover, it is possible that the spring packet will be displaced from its intended position in response to miniscule, asymmetrically applied forces and be positioned in the receiving bore in a lopsided manner. The correct functioning of the fuel injector will then no longer be ensured since the spring force acting on the valve-closure element may vary.